"With these results, we are not suggesting that people run out and buy and use grape seed extract. That could be dangerous since so little is known about doses and side effects," said Rajesh Agarwal of the University of Colorado Health Sciences Center in Denver.
"The value of this preclinical study is that it shows grape seed extract can attack cancer, and how it works, but much more investigation will be needed before these chemicals can be tested as a human cancer treatment and preventive."
The study, published in the journal Clinical Cancer Research, documented a 44-percent reduction of advanced colorectal tumors in the animals and also revealed, for the first time, the molecular mechanism by which grape seed extract works to inhibit cancer growth.
The authors found that it increases availability of a critical protein, Cip1/p21, in tumors that effectively freezes the cell cycle and often pushes a cancer cell to self destruct.